I got so big so quick with my 3rd I though there had to be twins in there always had to ask if there isnt another heart beat.... Never was and only had one baby girl... I think with the 3rd as your body has been there a few times before it goes staight to been round LOL.... I am always sick so there was no difference there the heat too could be knocking you around a bit as to why you are sicker this time or you could be just having a different sex to the last PG....